Characterization of Deep Groundwater Resources at Owens Lake, Inyo County, California

The Los Angeles Department of Water and Power (LADWP) is implementing a dust mitigation program to reduce emissions of fine particulates from over 50 square miles of the dry (terminal) Owens Lake bed in Inyo County, California. Historic total water use has exceeded approximately 80,000 acre-feet per year of high-quality water. With the goal of continuing dust control measures while conserving potable water, the LADWP has evaluated the use of deep groundwater under Owens Lake to supply a portion of the water demand for dust suppression. Methods of characterization of deep groundwater resources have included (1) compilation of existing data and development of a preliminary conceptual model, (2) identification of data gaps, (3) field data collection and revision of the conceptual model, and (4) development and use of a 3-dimensional groundwater model. Field data collection methods utilized include construction and testing of 28 deep clustered monitoring wells, borehole geophysics combined with seismic (reflection) data interpretation, and isotope measurements in groundwater to evaluate the source region of groundwater recharge and the age of the groundwater. The new data, combined with re-analysis of existing data, dramatically improved the hydrogeologic conceptual model for the study area by better defining the hydrostratigraphy, updating the location of key faults, improving estimates on the location and amounts of groundwater recharge, characterizing the interaction between groundwater and surface water, and evaluating sensitive resources such as springs, artesian wells, and domestic wells. The field program identified five discreet aquifer horizons formed by variable depositional environments as lake levels varied through geologic time. A 12-layer MODFLOW numerical groundwater model was developed and used to evaluate groundwater development alternatives and the associated effects on sensitive environmental elements. The model was also used to optimize future well locations, develop protocols for pumping and monitoring, and provide recommendations regarding new well locations.